Along with recent developments in materials and manufacturing technology of ELD which can provide brighter ELD, the use of ELD is expected in a wider industrial field. Among others, ELD of an organic dispersion type particularly draws a great attention for its modest manufacturing cost and excellent brightness.
FIGS. 4 and 5 illustrate a prior art ELD. FIG. 4 is a partly exposed bottom view, and FIG. 5 is a cross-sectional view taken along A--A line of FIG. 4. In these drawings, reference numeral 1 refers to a lower electrode made of aluminum film, 2 to a transparent electrode made by depositing an oxidized mixture of In and Sn on a transparent sheet, and 3 to a light emission layer made of powdered ZnS-Mn, ZnS-Cu, etc. They are put in lamination so as to locate the lower electrode 1 at the bottom, the transparent electrode 2 thereon and the light emission layer 3 on the top, and they form a light emission arrangement. Reference numerals 4 and 5 denote lead terminals made of a metal film of phosphor bronze. One lead terminal 4 is secured to a lower surface of the transparent electrode 2 by a conductive adhesive 6 of silver paste, whereas the other lead terminal 5 is secured to a lower surface of the lower electrode 1 by another drop of the same adhesive 6. The entire body of the light emission arrangement in the form of a lamination of the lower electrode 1, light emission layer 3 and transparent electrode 2 as well as inner end portions of the lead terminals 4 and 5 is sealed by a pair of upper and lower protective sheets 7 and 8 made of polyethylene or other hot-melt film. Opposed ends of the protective sheets 7 and 8 are joined together by heat-sealing or other method to protect the light emission arrangement against moisture or water. Outer ends of the lead terminals 4 and 5 in the exterior of the protective sheets 7 and 8 are soldered to lead wires (not shown) for electrically connecting the ELD to an outer circuit. On application of a voltage between the lower electrode 1 and transparent electrode 2 via the lead terminals 4 and 5, conductive adhesive 6 and others from the outer circuit, the light emission layer 3 emits light.
The prior art ELD uses the conductive adhesive 6 of silver paste to electrically and mechanically connect the lead terminals 4 and 5 to the electrodes 1 and 2, which silver paste, although excellent in electrical characteristic, is not sufficient in mechanical strength. Therefore, the prior art ELD is apt to invite a contact failure of the lead terminals 4 and 5 upon application of an external stress or heat shock. Beside this, the use of silver paste practically requires a process (not shown) of insulating the lead terminal 5 nearer to the lower electrode 1 from the transparent electrode 2, and also requires a specific attention during application of silver paste to prevent its overflow beyond its proper position. Thus the use of silver paste for connection of the lead terminals 4 and 5 involves various disadvantages.